What is the ruling on the prayer of one who experiences seminal discharge with urine after urination due to an enlarged prostate?

Perhaps the discharge is wady and not maniy. In any case, if it was maniy and discharged without the usual pleasure, then ghusl (definition) is not obligatory; only wudu' is required. Similarly, if it was wady, then only wudu' is required. If its discharge is recurrent, then the person is considered to have sils (incontinence) and must perform wudu' for each prayer at the beginning of its time.